I was so astounded when I read this thread I had to sign up to reply.
I've had Silver Spangled Hamburgs for 6 years now and I can't fathom why anyone would keep anything else. They are the perfect chicken IMO. They are gorgeous. They are an egg laying machine. I reckon 300 eggs a year and they keep it up for about 5 years before production starts to drop off. The eggs get bigger as the chook gets older. I am incubating some right now from 9 or 10 year old hens and they are large eggs.
OK, so they are not ideal for a petting zoo, lol! But they are friendly enough if you don't try to grab them. They love to help with the gardening. And any other backyard project you have on the go. And they will send a delegation to your back door if dinner is late! Not that they really need it, they are great foragers.
Hamburgs are robust and healthy. When bird flu hit the flock a couple years ago, I only lost one adult hamburg, out of about 20. All the others recovered within about 3 days. We won't talk about the casualties in the rest of the flock.
If you are planning to keep hamburgs, you will need a big back yard that they can free range in, and a night time lock up with a bit of a run and high perches. If you try and cage them they will not be happy. If you need to catch one, wait till it's almost dark and they get a bit dopey.
If a hamburg "goes off the lay" it means that they have found a new and more inaccessible (to you) hiding place for their eggs. The challenge for you is to find it and not to let on that you have found it. Always leave a couple eggs in the nest and don't let them see you collecting them. Same goes for the owner of the pullet who is not laying at 7 mos old! Check under sheds, in the compost bin, in the dog kennel, under thick prickly shrubs, anywhere but the nest box.
I have had several roosters since I started breeding hamburgs. Only one got aggressive. That was after I caught and sold 6 members of his harem. I had to relegate him to a large run with his favorite hen for a few months and he calmed down.
I have just acquired a black hamburg rooster. He's gorgeous! I'll be getting some black hamburg pullets for him.
I would highly recommend Hamburgs to anyone who has the space to keep them.